Automatic telephone system



Aug.26,1947. ERGOHREL 2,426,196i

l AUTOMATIC TELEPHONE SYSTEM 4 I Filed Dec. 2o, 1945 3 sheets-sheet 1 v HEMEL/70 :maga/myn@ n INVENTOR fir/P09900. l? 6060/?52 Aug. 26, 194,7.` F. P. GOHOREL 2,426,196.

AUTOMATIC, TELEPHONE SYSTEM Filed Deo. 2o, 1945 :5 sheets-sheet 2 INVENTOR Fam/Afm. Haal/afa Aug. 26; 1947. F. P. GOHOREL 2,426,196l

AUTOMATIC TELEPHONE SYSTEM Filed neg. 2o, 194s 4s Smets-sheet :s

NOM/Sd al om. Ehm ESQ Patented ug. 26, 19417y AUTOMATIC TELEPHONE SYSTEM Fernand P.y Gohorel, Sceaux, France, assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application December 20, 1943, Serial No. 514,931 In France November 3, 1938 7 Claims.

The present invention relates to new and useful improvements in automatic telephone systems, and more particularly those for inside networks or P. B. Xs in which the subscribers may communicate with subscribers of an outside network over one or more junction lines.

In accordance with the invention, the subscribers of the inside P. B. X network may be connected directly with the lines of the outside network without the aid of an operator, either when calling or when answering a call coming from the outside network and when the operator who deals with outside calls is absent.

Moreover, the subscribers of the inside network are ab-le during a conversation with the outside network to hold the outside lines and get i-nto communication with another P. B. X subscriber of the inside network, and after this communication either to reconnect with the outside line, or to transfer it to a second P. B. X subscriber without the aid of the P. B. X operator.

The P, B. X operator can either terminate the conversation between two subscribers of the inside network in order to connect one of them with an outside line, or she may enter as third party into a conversation in order to warn one of the subscribers that a communication intended for him is waiting on the outside line.

The various characteristics of the invention will nowclearly appear from the following description referring to the attached drawings which represent:

Fig. 1, the detailed diagram of a junction circuit of the automatic P. B. X;

Fig. 2, the detailed diagram of the equipment of a junction line with the outside network;

Fig. 3, the detailed circuit diagram of the equipment of the operators position at the P. B. X; and

Fig. 4, the manner in which Figs. 1, 2 and 3, are to be connected.

In the following descriptions the letter Rpreceding the number of a relay contact spring, indicates that the contact is closed by this spring when the relay is in the normal position (not energized), and the letter T indicates that the contact is closed by this spring when the relay is in the operative position (energized).

I shall now explain in detail the operation of the system.

Calling an inside station- Let us assume that the P. Bl. X subscriber PI wishes to call another P. B. X subscriber. When PI removes his handset, the following circuit is completed: earth, loutton DA in the normal position, contact C2 of the switch-hook, button A inthe normal position, spring I of relay A, wire m, rest contact and spring I of the relay B, upper non-inductive winding of relay B, winding of common relay C and battery.

Relay C is energized and operates its contacts.

2 I-n its spring I and its operative contact, it completes the following circuit: earth, RSI, R4I, spring I of relay C, and its work contact, contact of the rotary magnet C1, of the connector C01, rest contact of magnet C2 of nder Chei, resistance R2, R62, lower winding of relay 2 and battery.

In its spring 3 and the work contact associated therewith, relay 3 completes a circuit identical with that which has just been indicated for the third connector. In its springs 2 and 4, and their work contacts, it prepares the same circuits of the connectors 2 and 4, said circuits being completed in the example shown only if the connectors I and 3 are already busy.

It will be assumed that the connectors I and 3 are free. Y

The relay 2 of connector C01 is energized over its lower winding in the circuit previously indicated. In the same way relay 2 of connector Coc (not shown) is energized over a similar circuit completed by contact 3 of the relay C.

Relay 2 in pulling up completes in its contact T24 the following step-by-step circuit of the connector C01: earth, R3I, R4I, spring I of relay C and its work contact, T24, wiper e, bank bus bar e', of the connector C01, winding of magnet C1 and battery.

The magnet C1 will attract its armature and open its contact. The opening of said contact opens the circuit of the lower winding of relay 2 which falls back opening the circuit of magnet C1 which releases its armature. The wipers of C01 advance one step. When C1 releases its arma-.- ture, it recloses its contact and the circuit of the lower winding of relay 2 is again completed. This relay pulls up and closes the circuit of magnet C1.

It will be seen that under these conditions by the combination of the operation of relay 2 and of the opening of the contact of magnet C1, the wipers of the connector C01 will advance stepby-step. The advancement of the wipers of connector Cos is effected in the same manner.

When one of the wipers e of the connectors arrives on the bankV contact e", the following circuit is completed (the circuit of magnet C1 being open, the wipers of C01 remain in the position corresponding toe): battery, magnet C2 of the subscribers line finder C1161, bank contact e", wiper e of C01, T24, spring I of C, and its work contact R4I, RSI and earth.

Moreover, relay 5 is energized in the same circuit through its lower winding.

The operation of relay 2 and the closing and opening of the contact of magnet C2, will close and open the energization circuit of the magnet which causes the step-by-step advance of the wipers and nders Che1, in order to huntv for the calling subscribers line.

When the wipers of Chei arrive on the `bank contacts of the calling subscribers line, the fol-- lowing circuit is completed: earth, button DA of the station P, contact C2 of the switch-hook, button A normal, spring I of relay A and its rest contact, wire m, bank contact m, wiper fm of Chei, lower winding of stopping relay 3, T53, wiper ft, bank contact t, and battery through the lower winding of relay B.

The relays 3 and B are energized in series and 4the wipers of '0h61 are stopped, the energizing circuit of magnet Cz being opened at R3I. The circuit of relay 5 is also open and it falls back a moment after the energization of the relays 3 and B.

At TSI, relay 3 completes the circuit of the upper winding of relay 4, which pulls up and completes at T43 the holding circuit over the lower winding of relay 3.

The relay 2, the circuit of which is opened at R3I, remains in the normal position. The relay B opens through its spring I and its work contact the circuit of relay C, which falls back and thus releases the other connectors.

When relay 5 falls back, relay B is maintained attracted by earth on T44.

The line conductors a and b of the calling station P1 are connected to the windings of relay I through bank contacts a and b, the wipers fa, fb and T41 and T48. Relay I will be energized over the loop of the conductors a and b, .closed at station P1. The relay I closes through TI2 a circuit for the lower winding of relay 4, and through TI I, R63, T44, it closes the energizing circuit of relays V1 and V2.

The dial tone is sent to the :calling subscriber through: R65, R'I I, condenser Cm, T41, wiper fb and bank contact b, whereupon the calling subscriber P1 dials the desired subscribers number.

Each time the loop is opened at the station P1, relay I falls back and completes the following circuit for C1 of the connector C01: earth, T44, R53, RII, T45, R52, magnet C1 and battery.

' When relay I is again energized, the circuit of C1 is opened at TI I, magnet C1 releases its armature and the wipers of C01 advanced one step. The wipers will thus advance by a number of steps equal to the number of impulses transmitted by the dial of the subscriber P1. l

When P1 has finished dialling, the ringing of the desired subscriber is effected by operating button A which causes the opening of the circuit of relay 3. The relay 3 falls back and completes the following circuit: earth, RBI, T4I, upper winding of relay 6, RSI, wiper t of C01, bank contact of the desired. subscribers line, battery throughk the lower winding of relay B of the desired subscriber.

The relays- 6 and B (of the desired station) are energized and the buzzer 1' of the called station is operated over the circuit: earth, buzzer ro, contact C1 of the switch-hook in the position when the receiver is hung up, spring 2 of relay A and its* rest contact, wire a, bank contact of the connector C01, and wiper a, T65, R32, R22, T46 and battery through the winding of magnet C1 (magnet C1 cannot attract its armature when it is in series with the buzzer of a station).

The called subscriber hearing the buzzer, replies by removing his receiver. The circuit of relay 2 is completed over the called loop through T55, and T62, the wipers and bank contacts of the. connector C01. The` ringing circuit is opened at R22.

The calling and called subscribers'are now connected, the called subscribers receiver being fed through the winding of relay 2.

At the end of the conversation, when the subscribers hang up their receivers, relays I and 2 fall back, which causes the release of the connector and the other switches and relays.

Communications with main network Zines It will now be explained hoW a P. B. X subscriber may be connected with the outside network without the aid of the P. B. X operator, this facility being reserved for the so-called supplementary subscribers stations. A supplementary station has battery connected to the winding of its control relay A.

The calling subscriber P1 removes his receiver and the same operations take place, as in the previous case, until the sending of the dial tone to the subscriber P1.

The P. B. X subscriber dials the number allocated to the outside network. This causes the `controlled advance of the wipers of the connector C01, which are stopped on the bank contacts of an outside line.

The calling subscriber P1 operates button A of his set. The stopping relay 3 returns to normal vand completes the following circuit: earth, RBI,

T4I, upper winding of relay 6, RSI, wiper t of C01, bank contact t of the outside line, wire A, RQI, RIJI, Winding of relay 8, R94, R95, wire D, rest contact 2 of relays F2 and F3, wire P, wire I2, R22I, and battery through resistance R3. The relays 8 and 6 are energized.

The calling subscriber releases button A. Relay 3 is reenergized and earth on R3I is replaced by that on T6 I. By its contact T84, relay 8 closes the circuit of relay I2: battery, lower winding of relay I2, T84, contact of magnet C3 of the inder CheL, RIII, RSI, wire A, bank contact t o'l C01, wiper t, TSI and earth.

Relay I2 is energized and completes through TI2I the following circuit of magnet C3 of CheL: battery, winding of C3, TBI, TI2I, RI5, rest contact of thermostat TH, spring 4 of relay T and its rest contact RIS?, wire 2U, the out-of-order key in normal position, and earth.

Y The magnet C3 is energized, attracts its armature and opens its contact, which opens the circuit of relay I2, which falls back, thus opening the circuit of the magnet which releases its armature, causing the advance by one step by the wipers of CheL. The armature of C3 having returnedto normal, its contact is closed and the circuit of relay I2 is again completed, which causes a fresh energization of C3 and a fresh ad- Vance of the wipers, and so on.

The wipers of CheL thus advance step-by-step, hunting for the calling subscribers line. When the wipers arrive on the bank contacts corresponding to the calling line, the following circuit is completed: battery, winding of control relay A of the calling subscriber P1, bank contact t and corresponding wiper, T83, lower Winding of relay Iii, wiper and bank contact wire r, bank contact r of nder Chci, wiper je, T33, T54, wiper C of connector C01, bank contact C', spring I of relay F1 and. its work contact, and earth.

The relays A and I5 are energized in this circuit and. are maintained in the following circuit: earth on the rest contact of the button DA of station P1, contact Crv of lthe switch-hook of the station, rest contact of button A, spring I of relay A and its work contact, bank contact r and wiper of CheL, lower winding of relay I'il, T83, wiper of CheL, and bank contact T, Winding of A and battery.

Over the springs 2 and 3 of relay A and their work contact, the line conductors of the station P1 are connected to the network of Fig. 2. The nder CheL of said equipment is stopped, its circuit being opened at RI 05.

Relay Il is energized over its upper winding on the earth at TI34. Through TI'II relay I'I completes a holding circuit of relay A. Relay II is energized in series with relay III in the circuit: battery, winding of relay II, upper Winding of relay Ill, TI'I2, lower winding of relay Iii, wiper of CheL, and bank contact r, spring o of relay A and its work contact, button A, closed contact Cr of the switch-hook, button DA and earth.

Relay 9 is energized through its lower winding and earth on TIM. The relays l2 and 8 fall back, their circuit being opened when 9 pulls up. Through T32 relay 9 applies earth to the wire I l, which causes the lighting of th'e busy lamp at the operators position.

When the relay I1 pulls up, the conductors of the subscribers station P1 are connected through 'TI 'i3 and TVH to conductors A and B of the outside line.

, From that time the subscriber P1 may ring the called outside subscriber, the outside line being looped through station P1.

If the outside network is automatic, the subscriber P1 after having received the dialling tone dials the desired number. If the outside network is manual, the subscriber P1 indicates to the operator the number of the desired subscriber.

At the end of the conversation, when subscriber P1 hangs up his receiver, relays i3 and II fall back, their holding circuit being opened in the contact cr of the switch-hook, relays I'I and E! then fall back and the busy lamp of the P. B. X goes out.

When il falls back the loop of the outside line is opened at Tl'it and TI'Il, and the network is released. Moreover, the retraction of the relay ll causes the de-energization of control relay A.

If the outside network is manual, it is necessary to allow a certain amount of time to pass between the release of the line and the return to the subscribers disposal of the equipment for direct connection to the network, so that the operator of the exchange can see the end signal and proceed with' the disconnection. For this purpose when the previous circuit indicated by the rela-57 9 is opened at Ri'lfl, said relay remains attracted through its upper winding on the circuit: battery, upper winding of relay 9, T33, RISS, RI52, RIZI, RI25, contact of the thermostat TH, spring 4 of relay T and its rest contact.

The heating circuit of the thermostat is then completed through: battery, winding of thermostat TH, T93 and earth, through the previously traced circuit.

After a certain time of heating, the thermostat opens its Contact which has the eect of opening the circuit of relay a. Relay 9 falls back and through R3! connects the starting circuit to the equipment of Fig. 2.

In the case of an automatic outside network, the thermostat TH is eliminated. When P1 hangs up again all the elements return to normal and station P1 is again connected to the private automatic switch as soon as relay A falls back.

In the case of a manual outside network, the equipment for direct connection is completed by additional equipment for the transmission of different ringing or signalling currents.

Routing of a call coming from the outside network When a call is sent from the outside exchange through the line A-B it is received on the following circuit: line conductor A, RI92, winding of alternating current relay I6, R93, condenser C113, spring of relay T and its rest contact, RIM, line conductor A.

Relay I6 is energized and at TI 6I completes the circuit of relay I6 which pulls up and completes its holding circuit through: TIBZ', RI I2, thermostat TH, spring 4 of relay T and its rest contact, Ri?, wire 23 and earth on the trouble key.

Through its contact IGI relay I6 closes over wire l5 the circuit of the ringing lamp of th'e P. B. X of Pig. 3 through pilot relay P. At TI63 it closes the circuit of the lower winding of relay 9 which is energized, and at TQI switches the starting wire on the next finder.

The operator replies by depressing the network listening key. The following circuit is then completed: earth, spring 4 of relay R and its rest contact, switch-hook Cm of the operators set, work contact of the listening key, wire I9, RI85, winding of relay T, wire 24, lower winding of relay 23 and battery. i

Relays T and 23 are energized. Relay T applies earth' through TI3 to wire 25, thus completing the circuit of the upper Winding of relay 23 the windings of which, being in opposition, the relay falls back. Relay T remains attracted.

The P'. B. X operator of Fig. 3 is, from that time, in communication with the calling subscriber of the outside network through circuit: operators station PO, spring 'I of relay R and its rest contact, R263, R243, conductor II, spring Y 3 of relay T and its work contact, RI92, conductor A, outside exchange, conductor B, RI 94, spring S of relay T and its work contact, conductor I6, R2t2, R232, spring 8 of relay R and its rest contact, operators set P.

When the outside subscriber indicates the P. B. X subscriber With whom he wishes to talk, the P. B. X operator depresses the additional station key corresponding to the desired subscriber.

The following circuit is completed: earth, spring 4 of the relay R and its rest contact, work contact of the switch-hook Cm, wire 28, work contact of the additional station key, R234, R28I, R292, R30I, wire I3, spring Il] of relay T and its work contact, RIEII, winding of 8, T94, resistance RII and battery.

Moreover, the following circuit is also completed: battery, lower winding of holding relay I3, springs II 4and I0 of relay T .and their Work contact, wire I 8, and earth through the previously traced circuit.

Relay I9 is energized and holds the outside line by looping it over the resistance R4 through TI 9|. At RI92 and Rl 94 it disconnects the line from the P. B. X equipment.

Relay B is energized and closes at T84 the circuit of the lower Winding of relay I2 at RIUI and earth on wire I3, Relay I2 is energized and the following circuit of the rotary magnet C3 of finder CheL is completed: battery, winding of magnet C3, TSI, TI2I, RIGS, Contact of the thermostat TH, spring 4 of relay T and its work contact, wire 3, R232, R28I, R234 and earth on wire 28 through the depressed additional station key.

The magnet C3 is energized, attracts its armature -and by theplay relay I2, as previously explained, causes the advance of the Wipers of iinder .CheL. When the wipers of CheL arrive on the bank contacts corresponding to the desired P. B. X station, the following circuit is completed if the station is free: earth on wire 28, closed contact of the additional station key, wire I, bank Contact S of CheL, and the corresponding wiper, spring I of relay T and its work contact, wire 2, relay 22 and battery.

Relay 28 is energized and completes the following circuit for relay 33: battery, relay 33, R32 I RSI I, T28I, R32 and earth on wire 29 through the depressed additional station key.

At T33! relay 33 closes the circuit of the free lamp indicating to the operator that the desired P. B. X subscriber is free. Through T332 it completes the following circuit: earth, T332, wire 3, spring 6 of relay T and its work contact, upper winding ci relay I1 and battery.

Relay I1 is energized. Through TI'II it cornpletes the following circuit of the control relay A of the desired P. B. X station: earth, TI'II, wiper and bank contact T, control relay A and battery.

Relay A is energized and through its springs 2 and 3 connects station Pi to the conductors of the direct connection equipment through the wipers of CheL.

Through T'I'I, relay Il completes the following circuit: earth, T573, spring I3 of relay T and its Work Contact, resistance RIil, wire 2li, lower winding of relay 23 and battery.

The circuit of the upper winding of relay 23 is closed when free earth exists on wire 25, whiie its lower winding finds earth only through resistance RIG. The action of the upper winding is, therefore, effective and said relay attracts its armature.

Relay 33 falls back, its circuit being opened at R234. Relay I9 is held on the following circuit: earth, T235, spring 3 of relay R and its rest contact, depressed additional station key, wire 2I, upper Winding or relay I9 and battery.

Relay 29 is energized by earth on wire 23 through T2365 and the depressed additional sta-- tion key.

Relay Sli is energized in the circuit: battery winding of relay 34, wire 3, spring 5 of relay T and its work contact, TISS, wire 2|, depressed listen-in to network key, spring 3 of relay R, and its rest contact, T235 and earth.

The circuit of buzzer 23 of the desired station P1 is completed: battery, resistance R6, T29 I wire I'I, spring 3 of relay T and its work contact, THS, Wiper and bank contact a of Cheli, spring 2 of relay A and its work contact, contact C1 of the switch-hook in position with receiver hung up, buzzer 2] and earth.

Upon the reply of the subscriber P1 the operator can get in conversation with him over the following circuit: PO of the operators set, spring 'I of the relay R and its rest contact, R263, R263, wire I'I, springg of relay T and its work contact, TI'IS, wiper and bank contact a of CheL, spring 2 of relay A and its work contact, station P1, rest contact of the button R, spring 3 of relay A and its Work contact, bank contact b and wiper of CheL, TI 03, Till, spring 8 of relay T, and its work contact, wire I 3, R242, R262, spring 8 of relay R and its rest contact, operators set PO.

When the desired subscriber replies, the operator releases the additional station key, which causes the retraction of relay 29. The operators: set PO is then fed through the self-inductance 35 on the one hand, and on the other hand through T3152 and R29I.

The operator announces to the inside subscriber that she is going to connect him with an outside subscriber, and hangs up her set. The network listening returns to normal, which causes the retraction of the relays I9 and 35.

The connection between the additional station P1 and the outside line AB is established through RI92 and RIM.

If the P, B. X station were already engaged in a network communication when the operator depressed the additional station key of this station, relay 28 would pull up and relay 32 would be energized in the circuit: battery, winding of relay 32, R333, T 282, R232, wire li, spring 3 of relay T and its work contact T83, lower winding of relay I0, wiper and bank r of Che1, spring I of relay A and earth on button DA (normal). (The slewacting relay 33 does not have time to be energized before relay 32.)

The busy network lamp of st ation P1 lights up at the operators position through the circuit: battery, busy network lamp, TBM, REN, TZSI, R233, work contact of the depressed additional station key, and earth on wire 28.

The operator warns the outside calling subscriber and depresses the holding key corresponding to the calling network ine. She recalls the additional station P1 as soon as the busy network lamp is extinguished and completes the communication.

In the case in which the desired P. B. X sub- :scriber is busy with another P. B. X subscriber, the relay 28 will be energized. Owing to the fact that the desired subscribers line is busy on the private automatic switch, a free earth is applied to the wire t. Relay 3i is energized in the circuit: battery, winding of relay 3l, R333, T283, R23I, wire 3, spring 2 of relay T and its work contact, wiper and bank contact t of Cheli, and earth on wire t in the private automatic switch (the slow-acting relay 33 does not have time to pull up before the energization of relay l I l.

The local busy lamp of the operators set lights up in the circuit: battery, lamp, TSI I, TESL R232, closed contact of the additional station key, and earth on Wire 2S.

The operator may now either interrupt the lo- Cal connection and establish the network cornrnunication (oice cut-off), or she may warn the network line and advise the P. B. X station of the waiting communication by cutting-in as a third party on the local connection (offer of communication) I-f the operator wishes to cut the local connection, she depresses the oiiice cut-oil key, while maintaining the additional station key depressed.

Relay 33 is energized in the circuit: battery, winding of relay 33, R32 I, spring Ei of relay R and its rest contact, ofce cut-off key, T3I I, T28I, R234 and earth. At R333 it opens the circuit of relay 3I which falls back.

The operator releases the oilice cut-off key; relay 33 is held in the circuit: R32I, R3II, TSI, R23, closed contact of the additional station key, and earth on wire 28.

Through T332 relay 33 applies earth to wire Sl which, through spring 6 Of relay T and its Work contact, completes the circuit of the lower winding of relay Il. Relay Ii in pulling up completes the circuits which have just been described.

The P. B. X station P1 is connected by the springs 2 and 3 of relay A and their Work contact to the conductors of the equipment of Fig. 2. A busy signal is sent to the P. B. X subscriber with whom P1 was in communication, and P1 is connected to the outside subscriber when the operator hangs up her set,

If the operator wishes to warn the local subscriber that a communication intended for him is waiting on an outside line, she releases the additional station key and operates the key of one of the service lines, the key of the first service line, for example.

Relay 24 is energized through the key of the service line and on wire 28. The outside network line is held over T24I on the resistance R8, and the operators set PO is connected Vto the private automatic switch through T242, T243.

The P. B. X operator hears the dialling tone and dials the desired subscribers number.

The various operations in the private automatic switch take place in the same manner as in the case of connecting two P. B. X subscribers.

The relays I, 2, 3, 4 and 5 are energized, but relay 6 remains at normal, the desired subscriber already being engaged in an inside communication.

The operator then depresses the third party listening key, and the following circuit is completed: earth on the wire 28, monitoring key depressed, T241, wire e, bank and wiper fe of finder Che1, T33, R64, winding of relay 1 and battery.

Relay 1 pulls up and through T1I and T12 connects the operators set PO as a third party in the communication which is taking place through wipers of C01. The two P. B. X subscribers are warned that the operator is listening-in by the tone signal which they hear. The circuit of the vibrating relays V1 and V2 is closed through T44, R63 and TI I.

The operator oiers the outside communication.

to the desired subscriber. The P. B. X subscriber is connected with the outside line when the inside communication ends.

When a P. B. X subscriber is connected with the outside' network he can recall the P. B. X. operator by pressing button A, thus causing the temporary disconnection of the circuit of relay I which falls back and completes the following circuit of relay I3: battery, upper winding of relay I3, RI04, RBI', TI2I, RI05, contact on thermostat TH, spring 4 of relay T and its rest contact, RI81, wire 23, Contact of the trouble key (normal), and earth.

Relay I3 pulls up; through TI 32 it applies earth to wire 5 which completes the lighting of the ringing lamp; through its contact I3I it closes its holding circuit.

The operator seeing the lighting of the ringing lamp depresses the network listening key corresponding to the lamp. Relays T and 23 are energized and the following circuit of relay I9 is completed: battery, upper winding of I'El, wire 2|, network listening key (depressed), spring 3 of relay R and its rest contact, T235 and earth.

Line AB is cut 01T 'from the equipment at RISE and RI94 and the operator is connected with the P. B. X subscriber through springs 8 and 9 of relay T and their work contacts.

When the communication between the local subscriber and the operator is finished the subscriber is connected with the outside network when the operator hangs up her receiver.

I'he inside' subscriber, after having been put in communication with the operator, can ask her to pass the outside communication on to another inside subscriber.

The operator then depresses the trunk holding key and completes the following holding circuit for the relay I1: earth on the wire 28, trunk holding key in depressed position, T236, wire 22,

V1I) spring I2 of relay T, and its work contact TI35, TIIl3, lower winding of relay I1 and battery.

The P. B. X station which was in connection with the outside network hangs up and relays I0, II, I2, 23 and I9 fallback.

The operator is then in communication with the outside line and can make a fresh connection with a P. B. X subscriber in the same manner as when routing a call from an outside line.

Double call When a P. B. X subscriber is in communication with the outside network, he may hold the outside line, call another P. B. X subscriber, and then resume the communication with the outside subscriber.

In order to hold the line AB of the outside network and operate the private automatic switch, the subscriber presses button DA. Earth through resistance RI is substituted for the free earth on the rest contact of this button. The intensity of the current in the circuit of relays I0 and II is reduced and its new Value is such that relayv I0 is maintained attracted, but relay I I retracts. The following circuit is completed: battery, lower winding of relay I4, RI5I, R82, RI I I, TIIl5, contact of thermostat TH, spring 4 of relay T and its rest contact, RI81, wire 2i) and earth on the contact of the trouble key.

Relay I4 is energized and completes the following circuit: battery, upper windings in series of relays I4 and I5, RIMS, TI4I, TI14 and earth.

Relay I5 is energized in series with relay I4 and the two relays are maintained in thecircuit: battery, upper windings in series of relays i4 and I5, TISS, TI4I, TI14 and earth.` 1

Relay I9 is energized by its upper winding on earth at TI54, holds the outside line through TI9I on resistance R4,` and at RI92 and RI94 cuts oi the outside line AB from the P.. B. X equipment. g

If the rst double call line is free, relay 2I is energized on the circuit: earth, TI51, R203, windings of relay 2I in series, wire d", spring 3 of relay B", and its rest contact, resistance RIZ and battery.

If the rst double call line is engaged the relay B" pulls up and the relay 20 of the second double call line would be energized through the spring 4 of the relay B" and its work contact.

Relay 2| closes its holding circuit through T2I I, on its lower winding. Relay C is energized in the circuit: battery, winding of relay C, upper non-inductive winding of relay B", wire m", T2I2, TI58, TIIIZ and earth.

The station P1 is thus connected through the equipment of Fig. 1 over T2I1 and T2I8 and the double call line to the private automatic switch.

When relay C pulls up it starts the connector C01 and finder Che1.

When the wipers of Chei arrive on the bank contacts of the first double call line relay B pulls up on its lower winding in series with the lower winding of relay 3 stopping the finder.

The subscriber P1 'then proceeds to dial the number of the desired local subscriber. i

When the local conversation is nished and P1 wishes to be connected again with the outside,

l1 spring I of relay T` and. its rest contact, R-ISI, wirel 20 and' the earth on the trouble. key.

The winding of relay I4 being short-circuited, it falls back opening at R'IlII the holding circuit of I which falls back and opensY at TI 54 the holding circuit of relay I9, and through TI51 that of relay 2 I'.

When the relay I 9 falls back the local subscriber P1 is again put in connection through RI92 and RI94 with.v line. A-B of the outside network.

When relay 'l'.IA retracts, the line network. equipment of Fig.. 2` is cut on" fromk the private automatic switch which is thus released'.

It will now be explained how it is possible for aP. B. Xsubscriber in communication with an outside line toA transfer the connection to another P. B. X subscriber.

By means of a double call operation a P. l2.V X

station is selected to which the outside connec-A tion will be transferred'. The. outside line is held and the, P. B., X subscriber firstv calledl hangs up his receiver.

Relays Ill and II fall back and also relay I'I, of' which the holding circuit was completed through TI 04. Relay A ofw the rst called P. B. X station falls back, its circuit being opened at RI1I.

Relays I4 and I5 rem-ain energizedv on their lower windings through T2154 and earth on wire mf". The relay 9 is maintained attracted on its lower winding by.- earth on T2 I4.

The following circuit ofY relay I8' is completed: earth, T2I5, RI 1:5,.winding or relaytit, T95, wire D-spring 2 of relaysls and F3, and their rest contacts, wire; E, wire 12;. R221, resistance R3 and battery;

Through TI 83-relay appliesearth through T2 It to'wire S". Earth applied to Tllon wirey 2B replaces that of TI='I-4. for the holding of relays I4 and I5.

The following circuit is completed: earth', TZ I 5, RI'I.5, winding of relay IB, TI,8,I, wirey I4, winding of. relay- 30 and battery.

Relay 30 is energized in series with relay L8, and completes the following circuit of relays 8 and 22 which are energized in series.: earth, Winding of relay 22.,l Til,v wire I8., TIM,l RUBI, windingof relay 8, T94`resistance RII "and battery.

Through T84 relay 8 completes the circuit. of

relay I2 which is energized completing the following circuit. of magnet C3 of finder Cheli; battery, winding of magnet C3, T8 I', Tl2 I; RIDE, RI I2, TI88 and earth.

Magnet C3 by the play ofits contact and of relay I2 causes the advance of the wipers of CheL.

WhenA the Wipers of CheL arrive on the contact bank of the P. B. X' line` to whichthe transfer is to be effected the following circuit is completed: battery, relay A of the desired: P'. B. X'station, bank contact T and wiper off CiheL, T83, lower winding of relay: I0', wiper of Cheli and' bank contact 1?, wire r, bank contact r and wiper of the connector Col, T42', wiper fs of Chel, contact s", wire. s", T2 L6; TI83y andv earth.

Relays A and In are energized. Relay I'I is energized'. on earth applied at TIM.

Upon. the energization of relay A the second P. B. X stationv is connected by the springsA 2 and 3 and' their work contacts to the equipment of the network line, and consequently it' i's disconnected from the private automatic switch which returnsA to normal.

Relay I8 falls back, its circuit being opened 12 at RI15. Relays I4 andi I5- fall back, their holding circuit being opened bythe return to normal of spring'Z- of relay B.

Relays 2I and I9 fall back, and the second P. B. X station is connected with waiting outside line.

At the end of the communication the release 0f the network equipment is effected asA previously explained.

If for any reason the connection cannot be transferred either because the desired P. B, X station had not been warned or because he was busy, the following circuit is completed: earth, TI54, TIBB, winding of thermostat TH and battery.

The thermostat TH is heated and at the end of a certain time closes its contact which completes the circuit of the upper winding of relay I3 through RI33. Relay I3 completes its holding circuit on its lower winding through TI3I, RI I2, TI 88 and earth.

At RI33 relay |13 opens thev circuit of thermostat TEE', which cools again and opens its contact; at TI32- it applies earth to wire 5 which causes the lighting of the re-call lamp at the operators position.

The operator being warned gets onto the outside line, A-B andv deals with the waiting connection as itv seems to her best.

P. B. X subscribers may also answer directly outside calls without the intervention of the P. B; X operator who has depressedv the nightreturn key.

A second position is provided on the connectors Col for outside lines which may be reached by any P. B. X subscriber dialling the number of this position.

As in the previous case when. the operators station is in use, the ringing current received causes the energization of relays I3, I6".

At I6 I relay I6 closes the circuit of the ringing lamp. and of pilot relay P, which completes the circuit (not shown) of the ringing mechanism arranged at the P., B. X stations equipped for answering outside calls.

It will be assumed that the subscriber P1 is answering the outside call by dialling` the number corresponding to. the special position of Col whose wipers` will. be moved to the contacts t, e".

The subscriber Pi then presses, his button A. The stopping relay 3 returns to normal andthe following circuit. is completed-z earth, R3I, T4I, upperl winding ofY relay 6;, RBI., wiper tv of C01, bank contact 1?windingl of relay N, wire A', wire Il), contact of the night-return key, resistance R211 and battery.

Relays 6 and N" are energized. The subscriber P1 releases button A. Relay 3` is energized again and earth on wiper t through RSI is replaced by that of T6 I..

When relay I6 pullsup. it completes. at TISS the circuit ofthe lower winding of relay` 9l which is energized.

Relay N' in pulling up completes through its spring 2 and its work contact the following circuit of relay IB: earth, spring 2 of relay N and its work contact, wire B', T|.65.", RI'IS', winding of relay I8', T95, wire D, spring 2 of relays. F2 and Fs and their rest contact, wire F, wire. I2, R22I, resistance R3 and battery.

Relay I8 pulls up.

The followingcircuit of relays 30 and I8v is completed: battery, winding. of relay 30, wire I4, TI8I,

i3 winding of I8, Rll, TM5', B, spring 2 of relay N and its work contact.

Although relay 3@ is shunted by resistance B3 it pulls up and completes the following circuit of relays 8 and 22: earth, winding of relay 22, TSM, wire i8, Tini, Riti, winding oi relay t, T94, resistance Ril and battery.

Relays ii and 22 pull up. Through T84 relay il closes the energizing circuit of the lower Winding of relay l2. The energizing circuit of magnet C3 oi CheL is completed through: battery, winding of magnet C3, T36, Tizi, R965, BH2, TIM and earth.

By the play of relay lil and the Contact of magnet C2i the wipers of CheL advance step-by-step in search of the P. B. X line.

It will be noted that when relay N has pulled up Aearth. was applied to the bank contact r of CheL corresponding to the line of the subscriber P1 through the circuit: earth, closed contact of the key night-return, wire l, TIM', TISZ, wire C', spring i relay N and its work contact, bank contact C of Coi, wiper C, T64, T33, wiper je, of Che1, bank contact r of Cher, wire r, bank contact of r of CheL.

When the wipers of CheL arrive in the position corresponding to the line of the subscriber P1 the circuit of relays A and l@ is completed to the earth on the bank contact 1.

Relay l@ pulling up stops the wipers of CheL. At Tll it completes the circuit of the upper winding of relay Il which pulls up.

When relay A pulls up it transfers through its springs i and 3 the station P1 of the private automatic switch to the equipment of the network line. Through its spring i and its work contact relay A through the button DA, switch-hook Cr, button B and button A applies a fresh earth to the bank contact 1^ in order to replace that applied through spring l of relay N which will be eliminated when the private automatic switch is released.

After the retraction of of which the circuit has been opened at Riel, relay A is maintained on earth at Till and relays il and lll in series on earth at the bank contact r through Tl 12.

rlhe P. B. X subscriber P1 is in communication with the network line through THS- Till and Riez-REM.

At the end of the communication of release of the equipment of Fig. 2 is effected when the subscriber P1 hangs up his receiver.

It is, of course, understood that the embodiments have been given by way of non-limiting examples, and it would in particular be possible to combine all or some of them with more complicated embodiments, to replace certain elements or groups of elements by others, giving the same results and without departing from the scope of the invention.

What is claimed is:

1. In a telephone system, a plurality of subscribers lines, means including paired line finder and connector switches for interconnecting calling and called lines, each of said switches having brushes and stationary terminals cooperating therewith, means responsive to the initiation of a call to move the brushes of a connector, means operative thereupon for actuating the line iinder paired with the operated connector to seize the calling line, and means at the seized calling line for controlling over the line nder the brushes of the connector to select the called line.

2. In a telephone system, a plurality of subscribers lines, means including paired line nder 14 and connector switches for interconnecting calling and called lines, each of said switches having brushes and stationary terminals cooperating therewith, means responsive upon the initiation oi" a cal] to move the brushes of a plurality of connectors, means operative upon the selection of a certain terminal in one of the connectors for actuating the line nnder paired therewith to seize the calling line, means for releasing the other operated connectors, and means at the seized calling line for controlling over the line nader the paired connector to select the called line.

3. In a telephone system, a main exchange, a P. B. X, subscribers lines terminating at said eX- changes, trunks interconnecting said exchanges, paired line finder and connector switches in the P. B. X, means responsive to the initiation of a call on a P. B. X line for operating one of said connectors, means operative thereupon for actuating the line finder paired therewith to select the calling line and to connect it with the operated connector, means controlled by the calling subscriber for operating the last-mentioned connector to select the desired line, connections to said trunks selectable by said connectors, aspecial P, B. X switch in which each trunk terminates, P. B.'X subscribers lines connections selectable by the special switches, means controlled by a calling P. B. X station for operating the special switch in which the trunk terminates the selection of which it had controlled to connect the last-selected trunk with the calling P. B, X line, and means operative thereupon for releasing the operated nder and connector pair used in the selection of the trunk.

4. In a telephone system, a P; B. X, a main exchange, lines terminating at each exchange, trunks interconnecting said exchanges, an operators position at said P. B. X, line finder and connector switches at the P. B. X, means controlled by a. calling P. B. X subscriber for actuating a line iinder and a connector to establish connections between calling and called P. B. X lines and between a calling P, B. X line and one of said trunks, a plurality of special finders in the P. B. X, each having wipers in which a trunk terminates and terminals connected to the lines of certain P. B. X stations, means controlled by the operator for actuating the special finder on whose trunk a call comes in from the main eX- change for selecting a P. B. X station, and means controlled by the operator for actuating a line nnder and a connector for connecting a trunk with a P. B. X station.

5. In a telephone system, a P. B. X, a main exchange, lines terminating at each exchange, trunks interconnecting said exchanges, an operators position at said P. B, X, pairs of line finder and connector switches at the P. B. X, means controlled by a calling P. B. X subscriber and means controlled by the operator for actuating a pair of line nder and connector switches to establish connections between calling and called P. B. X lines and between a P. B. X line and one of said trunks, a plurality of special finders in the P. B. X, each having wipers in which a trunk terminates and terminals connected to the lines of certain stations, and means controlled by the operator for actuating the special finder on whose trunk a call comes in from the main exchange for selecting a P. B. X station.

6. In a telephone system, a main exchange, a P. B. X, lines terminating at said exchanges, trunks interconnecting said exchanges, line nd- 15 erl andv connector switches in said P. B. X for establishing connections between P. B. X subscribers. a special finder in the P. B. X for each trunk, means for operating said special finder for connecting a trunk with a. P. B. X station,

means controlled by a P, B. X station connected With-l a trunk over the special nder for holding said trunk and for connecting it with one of said lineA finders, means for operating the last-mentionedlinender to select said trunk, and means operative thereupon under the control of a P. B. X subscriber for actuating the connector associated. with the last-mentioned line finder to select aP; B. X station.

'7.` The system according to claim G and means 15 16 controlled by the last-mentioned P. B. X subscribers station for actuating the special finder connected with said trunk to connect therewith.

FERNAND P. GOHOREL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 1,812,222 Stich June 30, 1931 

